This invention relates to a co-extrusion apparatus in which two dissimilar materials are simultaneously extruded from respective extruder outlets.
One kind of co-extrusion apparatus has a pair of oval outlet openings juxtaposed to one another, each outlet communicating with a respective hopper via a respective passageway extending around the outside cylindrical surface of a respective rotatable drum. The rotation of the drums transports semi-solid material from the hoppers to the outlets. For forming a rope-like co-extrudate, a co-extrusion die is fastened to the co-extrusion apparatus at the outlets thereof, the die having an inner nozzle communicating with one of the outlets and an outer nozzle surrounding the inner nozzle and communicating with the other outlet of the co-extrusion apparatus. During operation of the co-extrusion apparatus, the rope-like co-extrudate is deposited upon a horizontally moving conveyor disposed below the mouth of the extrusion die.
The above-described co-extrusion apparatus is presently being used in the manufacture of cookies having an inner core formed of one substance and an outer envelope of another substance. For example, the inner substance might be a fruit filling or a dough having particulate matter such as nuts or chocolate chips, while the outer substance is another dough with or without particulate matter.
It has been found that the demand for a kind of cookie having an inner core of one material and an outer core of another, dissimilar material is not so great in some geographical areas as to require continuous manufacture of that cookie by co-extrusion apparatuses located in those areas. Moreover, it has been found that subsequently preparing the co-extrusion apparatus for the manufacture of another cookie having dissimilar inner and outer portions, in which at least one of the portions is different from the corresponding portion in the first cookie, results in consideration production inefficiencies owing to the time required to clean the co-extrusion apparatus for the new material.
An object of the present invention is to provide a method of using a co-extrusion apparatus in which the percentage of time that the apparatus is in use is increased and in which the down time of the co-extrusion apparatus is reduced.
Another object is to provide a die head utilizable in such a method to convert a co-extrusion apparatus from a co-extrusion to a simple extrusion mode of operation.